Certain pharmaceuticals can be administered in powdered form through inhalation of the powdered pharmaceutical down into the lungs. This type of pulmonary pharmaceutical delivery has several advantages. It eliminates the requirement for the use of needles and syringes, which many patients are uncomfortable with. Also, certain pharmaceuticals have a relatively short shelf life when in liquid form. Therefore, administration in powdered form may eliminate the necessity to reconstitute the pharmaceutical with a liquid diluent.
Although not all pharmaceutical products are suitable for being administered in powdered form, many pharmaceuticals have been formulated for pulmonary inhalation. For example, Novo Nordisk of Bagsvaerd, Denmark, sells a nasal insulin preparation which is inhaled by the user. Other types of pharmaceuticals are administered in powdered form as well. Another pharmaceutical for oral inhalation by asthmatic patients is sold by Glaxo of Bern, Switzerland. The medication is delivered by a device, sold as the DISKHALER.RTM., which has a rotatable disk with a number of regions containing pharmaceutical crystals. The disk is rotated to a position which brings one of the pharmaceutical-containing packets in line with a needle cannula; the needle cannula is then manipulated to puncture the packet to allow the pharmaceutical to be inhaled. Another type of powdered pharmaceutical delivery device is sold by Fisons Corporation of Bedford, Mass., under the trademark SpinHaler.RTM.. It uses a gelatin capsule containing the powdered pharmaceutical. The capsule is pierced by a needle which allows the pharmaceutical to be pulmonarily inhaled through the mouth and into the lungs.
One of the problems with prior art powdered pharmaceutical delivery devices is that the device is reused, as is normal for non-single user devices. The powdered pharmaceutical often clings to, coats or even cakes onto various surfaces of the device especially those in direct contact with the air stream surface of the device. These surfaces, which often have been moistened by the user's breath, can become distorted and contaminated; the contaminated surfaces may create additional health problems during subsequent use due to the proliferation of bacterial contamination.
Another problem with prior art powdered pharmaceutical delivery devices relates to the inability of physician and/or user to selectively vary the dose. That is, with conventional inhalers the dose is typically fixed so that, for example, the entire contents of a single capsule is administered to the user with each use. Also, conventional pharmaceutical inhalers are not typically constructed for the simultaneous intermixing and inhalation of two or more pharmaceutical components.
Finally, prior art powdered pharmaceutical inhalation devices are not able to accurately dose powdered pharmaceuticals in doses of less than 500 microgram volumes.